Fermentation and human brain expansion

The expansion of the human brain represents a metabolic paradox: how did our ancestors fuel such an energetically expensive organ while reducing the size of the digestive tract? While the "Cooking Hypothesis" suggests fire was the primary driver, the transition likely began much earlier. This talk will explore the External Fermentation Hypothesis, proposing that the intentional or accidental fermentation of foods could have provided a crucial "external stomach." By outsourcing the work of digestion to microbes, early hominids could access higher caloric density and more bioavailable nutrients. We will discuss how this shift in food technology may have predated fire, served as a catalyst for the initial surge in brain volume, and what it suggests about the unique evolutionary trajectory of the human lineage.